drbd: split off drbd_config into separate file

To be more similar to what we do in the out-of-tree module and ease the
upstreaming process.

Signed-off-by: Christoph Böhmwalder <christoph.boehmwalder@linbit.com>
Reviewed-by: Joel Colledge <joel.colledge@linbit.com>
Link: https://lore.kernel.org/r/20230113123506.144082-4-christoph.boehmwalder@linbit.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>

include/linux/drbd_config.h

@@ -0,0 +1,16 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * drbd_config.h
+ * DRBD's compile time configuration.
+ */
+
+#ifndef DRBD_CONFIG_H
+#define DRBD_CONFIG_H
+
+extern const char *drbd_buildtag(void);
+
+#define REL_VERSION "8.4.11"
+#define PRO_VERSION_MIN 86
+#define PRO_VERSION_MAX 101
+
+#endif